For the first time, climate change has caused a river to completely reroute

For the first time on record, climate change has completely changed the route of a river. In a shift that researchers called “geologically instantaneous,” a river in Canada’s Yukon territory shifted from draining into the Bering Sea to draining into the Pacific Ocean below Alaska. What makes this particularly concerning is that while shifting rivers aren’t unheard of in the Earth’s history, never before to our knowledge has a river rerouted so quickly, causing an enormous impact on the surrounding environment.

The Kaskawulsh glacier in Canada has been rapidly melting. That influx of meltwater choked out the Slims River, depriving the downstream Kluane Lake of water and causing it to drop rapidly. The water shifted to the Alsek River, which empties into the Pacific Ocean south of Alaska, where the ocean water will now see a rapid influx of freshwater. The shift began in 2016 when the melting water burst through an ice dam, depriving Slims River of its glacial water source. Now, the Kluane Lake level is dropping rapidly, which will put stress on the environment around the lake and could completely alter the geology of the area.

Scientists determined that this shift was driven by human-caused climate change after they looked at the Kaskawulsh glacier and calculated that there was only a minuscule chance of it retreating in a stable climate. They also believe that it is unlikely that the Slims River will return to its previous water levels. The researchers published their findings in the journal Nature Geoscience.